- Which of the following techniques is used to amplify a specific DNA sequence?
a) Gel electrophoresis
b) Polymerase chain reaction (PCR)
c) Southern blotting
d) DNA sequencing
Answer: b) Polymerase chain reaction (PCR)
Explanation: PCR is a technique used to amplify a specific DNA sequence by repeatedly heating and cooling the sample to denature the DNA, anneal primers, and extend the new DNA strand using a DNA polymerase.
- What is the role of DNA helicase during DNA replication?
a) Synthesizing new DNA strands
b) Adding RNA primers to the template strand
c) Unwinding the double-stranded DNA helix
d) Connecting Okazaki fragments on the lagging strand
Answer: c) Unwinding the double-stranded DNA helix
Explanation: DNA helicase unwinds the double-stranded DNA at the replication fork by breaking the hydrogen bonds between the complementary bases, allowing the DNA polymerase to access the template strands for replication.
- Which of the following RNA types is involved in carrying genetic information from DNA to the ribosome for protein synthesis?
a) mRNA
b) tRNA
c) rRNA
d) siRNA
Answer: a) mRNA
Explanation: Messenger RNA (mRNA) carries the genetic code transcribed from DNA to the ribosome, where it is translated into a specific sequence of amino acids to form a protein.
- Which of the following is a characteristic feature of a codon?
a) It is made up of four nucleotides
b) Each codon is recognized by an anticodon on tRNA
c) There are 64 stop codons
d) All amino acids are coded by a single codon
Answer: b) Each codon is recognized by an anticodon on tRNA
Explanation: Codons are sequences of three nucleotides on mRNA that correspond to specific amino acids. Each codon is recognized by a complementary anticodon on tRNA, which brings the correct amino acid during translation.
- Which type of DNA sequence in eukaryotes is typically involved in regulating gene expression by silencing transcription?
a) Exons
b) Promoters
c) Enhancers
d) Silencers
Answer: d) Silencers
Explanation: Silencers are regulatory DNA sequences that bind to repressor proteins, inhibiting transcription and decreasing gene expression. Enhancers, in contrast, increase the transcription of associated genes.
- Which of the following enzymes catalyzes the synthesis of DNA from an RNA template in retroviruses?
a) RNA polymerase
b) DNA polymerase
c) Reverse transcriptase
d) DNA ligase
Answer: c) Reverse transcriptase
Explanation: Reverse transcriptase is an enzyme found in retroviruses that catalyzes the synthesis of DNA from an RNA template, allowing the viral RNA genome to integrate into the host DNA.
- The process of removing introns and joining exons in a pre-mRNA transcript is called:
a) RNA capping
b) RNA splicing
c) RNA interference
d) Polyadenylation
Answer: b) RNA splicing
Explanation: RNA splicing is the process by which non-coding introns are removed from a pre-mRNA transcript, and coding exons are joined together to form the mature mRNA that will be translated into a protein.
- Which of the following best describes the function of telomerase in eukaryotic cells?
a) It repairs mismatched bases during DNA replication
b) It shortens telomeres during each round of cell division
c) It adds repetitive nucleotide sequences to the ends of chromosomes
d) It prevents the unwinding of DNA during replication
Answer: c) It adds repetitive nucleotide sequences to the ends of chromosomes
Explanation: Telomerase is an enzyme that adds repetitive nucleotide sequences to the ends of chromosomes (telomeres) to prevent their shortening during DNA replication, maintaining chromosome stability.
- In eukaryotic cells, transcription takes place in the:
a) Cytoplasm
b) Mitochondria
c) Nucleus
d) Ribosomes
Answer: c) Nucleus
Explanation: In eukaryotic cells, transcription (the process of synthesizing RNA from DNA) occurs inside the nucleus, while translation (protein synthesis) takes place in the cytoplasm at the ribosomes.
- Which of the following correctly defines a frameshift mutation?
a) A mutation that results in a premature stop codon
b) A point mutation that changes one amino acid
c) A deletion or insertion of nucleotides that changes the reading frame
d) A mutation that does not alter the amino acid sequence
Answer: c) A deletion or insertion of nucleotides that changes the reading frame
Explanation: A frameshift mutation occurs when nucleotides are inserted or deleted from the DNA sequence, altering the reading frame of the genetic code, which can result in an entirely different protein being synthesized.
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